Strain enhancement for FinFETs

ABSTRACT

An integrated circuit device includes a substrate having a first portion in a first device region and a second portion in a second device region. A first semiconductor strip is in the first device region. A dielectric liner has an edge contacting a sidewall of the first semiconductor strip, wherein the dielectric liner is configured to apply a compressive stress or a tensile stress to the first semiconductor strip. A Shallow Trench Isolation (STI) region is over the dielectric liner, wherein a sidewall and a bottom surface of the STI region is in contact with a sidewall and a top surface of the dielectric liner.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.15/220,989, entitled “Strain Enhancement for FinFETs,” filed on Jul. 27,2016, which is a divisional of U.S. patent application Ser. No.14/153,632, entitled “Strain Enhancement for FinFETs,” filed on Jan. 13,2014, now U.S. Pat. No. 9,419,134 issued Aug. 16, 2016, whichapplications are incorporated herein by reference.

BACKGROUND

Reductions in the size and inherent features of semiconductor devices(e.g., a metal-oxide semiconductor field-effect transistor) have enabledcontinued improvement in speed, performance, density, and cost per unitfunction of integrated circuits over the past few decades. In accordancewith a design of the transistor and one of the inherent characteristicsthereof, modulating the length of a channel region underlying a gatebetween a source and drain of the transistor alters a resistanceassociated with the channel region, thereby affecting the performance ofthe transistor. More specifically, shortening the length of the channelregion reduces a source-to-drain resistance of the transistor, which,assuming other parameters are maintained relatively constant, may allowan increase in current flow between the source and drain when asufficient voltage is applied to the gate of the transistor.

To further enhance the performance of MOS devices, stress may beintroduced in the channel region of a MOS transistor to improve carriermobility. Generally, it is desirable to induce a tensile stress in thechannel region of an n-type metal-oxide-semiconductor (“NMOS”) device ina source-to-drain direction and to induce a compressive stress in thechannel region of a p-type MOS (“PMOS”) device in a source-to-draindirection.

A commonly used method for applying compressive stress to the channelregions of PMOS devices is to grow SiGe stressors in the source anddrain regions. Such a method typically includes the steps of forming agate stack on a semiconductor substrate, forming spacers on sidewalls ofthe gate stack, forming recesses in the silicon substrate along the gatespacers, epitaxially growing SiGe stressors in the recesses, and thenannealing. Since SiGe has a greater lattice constant than silicon has,it expands after annealing and applies a compressive stress to thechannel region, which is located between a source SiGe stressor and adrain SiGe stressor. Similarly, stresses can be introduced to thechannel regions of NMOS devices by forming SiC stressors. Since SiC hasa smaller lattice constant than silicon has, it contracts afterannealing and applies a tensile stress to the channel region.

The MOS devices formed from conventional stressor formation processessuffer leakage problems, however. To apply a greater stress to thechannel region, the stressors need to have high germanium or carbonconcentrations. High germanium or carbon concentrations in turn causehigh defect concentrations, and thus cause an increase in junctionleakage and a decrease in breakdown voltage. Accordingly, new methodsfor improving the stressor formation processes are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIGS. 1 through 8 are cross-sectional views of intermediate stages inthe formation of Fin Field-Effect Transistors (FinFETs) with stressedfins in accordance with some exemplary embodiments;

FIGS. 9 through 17 are cross-sectional views of intermediate stages inthe formation of FinFETs with stressed fins in accordance withalternative embodiments;

FIGS. 18 through 26 are cross-sectional views of intermediate stages inthe formation of FinFETs with stressed fins in accordance withalternative embodiments, wherein lower STI regions are formed before theformation of stressed regions; and

FIGS. 27 through 36 are cross-sectional views of intermediate stages inthe formation of FinFETs with stressed fins in accordance withalternative embodiments, wherein lower STI regions are formed before theformation of stressed regions.

DETAILED DESCRIPTION

The making and using of the embodiments of the disclosure are discussedin detail below. It should be appreciated, however, that the embodimentsprovide many applicable concepts that can be embodied in a wide varietyof specific contexts. The specific embodiments discussed areillustrative, and do not limit the scope of the disclosure.

Complementary Fin Field-Effect Transistors (FinFETs) and the method offorming the same are provided in accordance with various exemplaryembodiments. The intermediate stages of forming the FinFETs areillustrated. The variations of the embodiments are discussed. Throughoutthe various views and illustrative embodiments, like reference numbersare used to designate like elements.

FIGS. 1 through 8 illustrate the cross-sectional views of intermediatestages in the manufacturing of Fin Field-Effect Transistors (FinFETs) inaccordance with some embodiments. Referring to FIG. 1, wafer 2 isprovided. Wafer 2 includes substrate 10, which may be a semiconductorsubstrate in some embodiments. Substrate 10 may be a silicon substrate,a germanium substrate, a silicon germanium substrate, a III-V compoundsemiconductor substrate, or the like. Wafer 2 includes a portion indevice region 100, and a portion in device regions 200. Device regions100 and 200 are used to form a p-type FinFET and an n-type FinFET. Insome embodiments, device region 100 is for forming the p-type FinFET,and device region 200 is for forming the n-type FinFET. In alternativeembodiments, device region 100 is for forming the n-type FinFET, anddevice region 200 is for forming the p-type FinFET.

Referring to FIG. 2, substrate 10 is etched to form trenches 14, withsemiconductor strips 12, which are parts of substrate 10, left betweentrenches 14. Depth D1 of trenches 14 may be in the range between about100 nm and about 170 nm. It is appreciated, however, that the valuesrecited throughout the description are merely examples, and may bechanged to different values. The etching may be performed using aSiCoNi-based gas. After the formation of trenches 14, a pre-treatmentmay be performed. The pre-treatment is performed at a temperature in therange between about 400° C. and about 1,200° C. in some embodiments. Thetreatment gas may include oxygen (O₂), water steam (H₂O), nitrogen (N₂),or the like. As a result of the pre-treatment, a thin film (not shown)may be formed on the exposed surfaces of semiconductor strips 12. Thethin film may include an oxide, a nitride, or the like, wherein thematerial of the thin film depends upon the material of substrate 10 andthe process gas used in the pre-treatment. In some embodiments, thepre-treatment is a thermal treatment performed at a temperature in therange between about 400° C. and about 1,200° C. In alternativeembodiments, the treatment includes a Ultra-Violet (UV) treatment usinga UV light with a wavelength in the range between about 200 nm and about400 nm. In yet alternative embodiments, the pre-treatment includes amicrowave treatment using a microwave with a wavelength greater thanabout 1 mm. During the pre-treatment, wafer 2 may be heated (forexample, to the above-referenced temperatures) or at a room temperature(such as about 21° C.).

FIG. 3 illustrates the formation of dielectric liner 16, which is formedusing a deposition method and/or an oxidation or a nitridation method.Dielectric liner 16 may be a single homogenous layer or a compositelayer, and may include a silicon nitride (Si₃N₄) layer, a silicon oxide(SiO₂) layer, an aluminum oxide (Al₂O₃) layer, or multi-layers thereof.Dielectric liner 16 may also have a high Young's modulus, for example,higher than about 100 G Pa. The respective material with the highYoung's modulus may include SiON, SiN, or Si₃N₄, for example. Thethickness of dielectric liner 16 (and each of the silicon nitride layer,the silicon oxide layer, and the aluminum oxide layer) may be in therange between about 1 nm and about 5 nm. In some exemplary embodiments,the formation of the silicon nitride layer is performed using ChemicalVapor Deposition (CVD), Atomic Layer Deposition (ALD), Molecular LayerDeposition (MLD), or the like. The deposition temperature may be in therange between about 300° C. and about 700° C., with plasma turned on toassist the deposition. The precursor may include SiH₄, Dichloro-Silane(DCS), NH₃, and/or the like. In some exemplary embodiments, theformation of the silicon oxide layer is performed using CVD, ALD, or thelike. The deposition temperature may be in the range between about 300°C. and about 700° C., with plasma turned on to assist the deposition.The precursor may include SiH₄, DCS, N₂O, H₂O, O₂, and/or the like. Insome exemplary embodiments, the formation of the aluminum oxide layer isperformed using ALD. The deposition temperature may be in the rangebetween about 500° C. and about 600° C. The precursor may include AlH₃,H₂O, and the like.

After the formation of dielectric liner 16, a treatment is performed. Insome embodiments, the treatment is performed using a thermal treatment,a UV treatment, or a microwave treatment, wherein the process conditionsmay be selected from the candidate process conditions for thepre-treatment, which is performed before dielectric liner 16 is formed.For example, the treatment gas may include oxygen (O₂), water steam(H₂O), nitrogen (N₂), or the like. When the thermal treatment isperformed, the temperature may be in the range between about 400° C. andabout 1,200° C. When the UV treatment is used, the UV light may have awavelength in the range between about 200 nm and about 400 nm. When themicrowave treatment is used, the wavelength may be greater than about 1mm.

By adjusting formation process conditions, the material, and thetreatment conditions of dielectric liner 16, dielectric liner 16 mayapply a compressive stress, a tensile stress, or a neutral stress.Throughout the description, when a compressive stress or a tensilestress applied on semiconductor strips 12 is referred to, thecompressive stress or the tensile stress has a magnitude higher thanabout 300 MPa. Furthermore, when a neutral stress is referred to, theneutral stress refers to no stress or stresses with stress magnitudesmaller than about 300 MPa. In some exemplary embodiments, to makedielectric liner 16 to apply a compressive stress to semiconductorstrips 12, dielectric liner 16 comprises tensile silicon nitride, andthe respective formation process and/or treatment process compriseChemical Vapor Deposition (CVD) at 400° C., followed by a Ultra-Violet(UV) curing. In some alternative embodiments, to make dielectric liner16 to apply a tensile stress to semiconductor strips 12, dielectricliner 16 comprises compressive silicon nitride, and the respectiveformation process and/or treatment process comprises CVD at 400° C.,with no UV curing performed. In yet alternative embodiments, to makedielectric liner 16 to apply a neutral stress to semiconductor strips12, dielectric liner 16 comprises silicon nitride, and the respectiveformation process and/or treatment process comprise CVD at 400° C.,wherein the process gas has higher NH₃ flow rate than the flow rates forforming tensile and compressive silicon nitrides. In yet alternativeembodiments, to make dielectric liner 16 to have the high Young'smodulus, dielectric liner 16 comprises Al₂O₃, silicon nitride, or thelike, and the respective formation process and/or treatment processcomprise Atomic Layer Deposition (ALD), Molecular Layer Deposition(MLD), CVD, or the like.

Next, referring to FIGS. 4 and 5, dielectric liner 16 is removed fromdevice region 200, and is left in device region 100. Referring to FIG.4, photo resist 18 is formed and patterned to cover the portion ofdielectric liner 16 in device region 100, while the portion ofdielectric liner 16 in device region 200 is removed. Next, the exposeddielectric liner 16 is removed, for example, using a SiCoNi gas. Theetching is symbolized by arrows 21. Photo resist 18 is then removed, asshown in FIG. 5.

FIG. 5 also illustrates the filling of dielectric material 20.Dielectric material 20 may be formed of a homogenous material, or mayinclude more than one layer formed of different materials or formedusing different methods. A planarization such as a Chemical MechanicalPolish (CMP) is performed to level the top surface of dielectricmaterial 20 with the top surfaces of dielectric liner 16 or the topsurfaces of semiconductor strips 12. The remaining dielectric material20 forms Shallow Trench Isolation (STI) regions 20. In some embodiments,dielectric material 20 includes an oxide, which is silicon oxide in someembodiments. Dielectric material 20 may be formed using FlowableChemical Vapor Deposition (FCVD), spin-on, or the like.

After the filling of dielectric material 20, and before or after theCMP, a treatment is performed on dielectric material (STI regions) 20.The treatment may be performed using a thermal treatment, a UVtreatment, a microwave treatment, or the like, wherein the processconditions may be selected from the candidate methods and candidateprocess conditions for the treatment (as shown in FIG. 3) of dielectricliner 16. In addition, when the treatment is used, the treatment may beperformed at a temperature lower than the treatment temperature ofdielectric liner 16. In some exemplary embodiments, the treatmenttemperature of STI regions 20 is lower than the treatment temperature ofdielectric liner 16 by a temperature difference greater than about 100°C.

STI regions 20 may by themselves apply a compressive stress, a tensilestress, or a neutral stress (no stress) to the adjoining semiconductorstrips 12 in device region 200. On the other hand, in device region 100,STI regions 20 and dielectric liner 16 in combination apply a stress(referred to as combined stress throughout the description, which may bea compressive stress, a tensile stress, or a neutral stress) to theadjoining semiconductor strips 12. Accordingly, the different schemes ofdielectric liner 16 and STI regions 20 may generate desirable stresscombinations for p-type FinFET and n-type FinFET.

For example, if device region 100 is an n-type FinFET region and deviceregion 200 is a p-type region, then it is desirable that the stressapplied to the semiconductor strips 12 in device region 100 is moretoward tensile direction than the stress applied to the semiconductorstrips 12 in device region 200. In some embodiments, dielectric liner 16may apply a tensile stress, and STI regions 20 may apply a tensilestress, a compressive stress, or a neutral stress to the adjoiningsemiconductor strips 12. The combined stress applied to semiconductorstrips 12 in device region 200 may be a tensile stress, a neutralstress, or a compressive stress. Alternatively, dielectric liner 16 hasthe high Young's modulus, for example, higher than about 100 GPa, andSTI regions 20 apply a compressive stress. Accordingly, dielectric liner16, due to the high Young's modulus, blocks (at least partially) orreduces the compressive stress from being applied to the semiconductorstrips 12 in device region 100, while the semiconductor strips 12 indevice region 200 receive the compressive stress.

Alternatively, if device region 100 is a p-type FinFET region and deviceregion 200 is an n-type region, then it is desirable that the stressapplied to the semiconductor strips 12 in device region 100 is moretoward compressive direction than the stress applied to thesemiconductor strips 12 in device region 200. In some embodiments,dielectric liner 16 applies a compressive stress, and STI regions 20apply a tensile stress, a compressive stress, or a neutral stress to theadjoining semiconductor strips 12. The combined stress applied tosemiconductor strips 12 in device region 200 may be a tensile stress, aneutral stress, or a compressive stress. Alternatively, dielectric liner16 has the high Young's modulus, for example, higher than about 100 GPa,and STI regions 20 apply a tensile stress. Accordingly, dielectric liner16, due to the high Young's modulus, blocks (at least partially) orreduces the tensile stress from being applied to the semiconductorstrips 12 in device region 100, while the semiconductor strips 12 indevice region 200 receives the tensile stress.

Next, as shown in FIG. 7, STI regions 20 and dielectric liner 16 arerecessed, for example, through a wet etching or a dry etching step. Therecessing depth D2 may be between about 20 nm and about 40 nm in someembodiments. Accordingly, the portions of semiconductor strips 12 overthe top surfaces of remaining STI regions 20 are referred to assemiconductor fins 22, which include fins 22A in device region 100 andfins 22B in device region 200.

FIG. 8 illustrates the formation of gate dielectrics 24 (including 24Aand 24B in device regions 100 and 200, respectively). Gate electrodes 26(including 26A and 26B) are formed over gate dielectrics 24A and 24B,respectively. Gate dielectrics 24 may include oxide, nitride, high-kdielectrics, or the like. Gate electrodes 26 may include polysilicon,metal or metal alloys, metal silicides, or the like. In subsequentprocess steps, source and drain regions (not shown) are formed in eachof device regions 100 and 200 to finish the formation of FinFETs 128 and228 in device regions 100 and 200, respectively. One of FinFETs 128 and228 is a p-type FinFET, and the other is an n-type FinFET. The desirablestresses in semiconductor fins 22 are related to the conductivity typesof FinFETs 128 and 228, wherein the fins 22 of the n-type FinFET is moretensile than the fins 22 of the p-type FinFET. The desirable stressesare achieved using the methods provided in preceding paragraphs.

FIGS. 9 through 36 illustrate cross-sectional views of intermediatestages in the formation of complementary FinFETs in accordance withalternative embodiments. Unless specified otherwise, the materials andthe formation methods of the components in these embodiments areessentially the same as the like components, which are denoted by likereference numerals in the embodiments shown in FIGS. 1 through 8. Thedetails regarding the formation process and the materials of thecomponents shown in FIGS. 9 through 36 may thus be found in thediscussion of the embodiment shown in FIGS. 1 through 8.

FIGS. 9 through 17 illustrate the formation of complementary FinFETs inaccordance with some embodiments. The initial steps of these embodimentsare essentially the same as shown in FIGS. 1 and 2. Next, as shown inFIG. 9, dielectric liner 16 is formed. In subsequent discussion of theembodiments in FIGS. 9 through 17, it is assumed that device region 100is an n-type FinFET region, and device region 200 is a p-type FinFETregion. Dielectric liner 16 may apply a tensile stress or a neutralstress to adjoining semiconductor strips 12. Alternatively, dielectricliner 16 has a high Young's modulus. The materials and the formationdetails for forming the tensile-stress applying dielectric liner 16, theneutral-stress applying dielectric liner 16, or dielectric liner 16 withhigh Young's modulus may be found in the description of the embodimentsin FIGS. 1 through 8.

FIGS. 10 and 11 illustrate the removal of dielectric liner 16 fromdevice region 200. In FIG. 10, photo resist 18 is formed in deviceregion. Next, photo resist 18 is used as an etching mask to etchdielectric liner 16 from device region 200. As shown in FIG. 11, photoresist 18 is removed.

Next, as shown in FIGS. 12 through 14, dielectric liner 16′ is formed indevice region 200, and is removed from device region 100. As shown inFIG. 12, dielectric liner 16′ is blanket formed in device regions 100and 200. Dielectric liner 16′ may apply a compressive stress or aneutral stress to semiconductor strips 12. Alternatively, dielectricliner 16′ has a high Young's modulus. The materials and the formationdetails for forming the compressive-stress applying dielectric liner16′, the neutral-stress applying dielectric liner 16′, or the dielectricliner 16′ with high Young's modulus are selected from the candidatematerials and formation process details for forming dielectric liner 16,which may be found in the description of the embodiments in FIGS. 1through 8.

Referring to FIG. 13, photo resist 18′ is formed in device region 200.Next, photo resist 18′ is used as an etching mask to etch dielectricliner 16′ from device region 100. As shown in FIG. 14, photo resist 18′is removed, leaving dielectric liners 16 and 16′ in device regions 100and 200, respectively. The subsequent process steps for finishing theformation of FinFETs 128 and 228 are shown in FIGS. 15 through 17. Theprocess details of the subsequent processes may be found in theembodiments shown in FIGS. 1 through 8, and are not repeated herein.

As shown in FIG. 17, dielectric liners 16 and 16′ are formed in deviceregions 100 and 200, respectively. Dielectric liners 16 and 16′ aredifferent from each other, and hence result in the stress applied to thefins 22A of the n-type FinFET (for example, 128) and the fins 22B of thep-type FinFET (for example, 228) to be different from each other. Forexample, when FinFETs 128 and 228 are n-type FinFET and p-type FinFET,respectively, dielectric liners 16 and 16′ cause the stress applied tothe fins 22A of n-type FinFET 128 to be more toward tensile directionthan the stress applied to the fins 22B of p-type FinFET 228. In someembodiments, dielectric liner 16 applies a tensile stress to therespective fins 22A, and dielectric liner 16′ applies a compressivestress to the respective fins 22B. In these embodiments, STI regions 20may apply a tensile stress, a compressive stress, or a neutral stress tofins 22. In alternative embodiments, dielectric liner 16 has a highYoung's modulus, and hence blocks the stress of STI regions from beingapplied on fins 22A, and dielectric liner 16′ applies a compressivestress to the respective fins 22B. In these embodiments, STI regions 20apply a compressive stress to fins 22. In yet alternative embodiments,dielectric liner 16 applies a tensile stress to the respective fins 22A,while dielectric liner 16′ has a high Young's modulus, and hence blocksthe stress of STI regions 20 from being applied on fins 22B. In theseembodiments, STI regions 20 apply a tensile stress to fins 22.

FIGS. 18 through 26 illustrate the formation of complementary FinFETs inaccordance with yet alternative embodiments. These embodiments areessentially the same as in the embodiments in FIGS. 1 through 8, exceptthat before the formation of dielectric liner 16 and STI regions 20,lower STI regions 30 are formed to fill the bottom portions of trenches14, leaving the top portions of trenches 14 not filled. By filling thebottom portions of trenches 14 with STI regions 30, dielectric liner 16is formed in the trenches with a smaller aspect ratio than the trenchesin the embodiments in FIGS. 1 through 8. The horizontal portions ofdielectric liners are thus closer to the overlying semiconductor fins,and the stresses applied by dielectric liner 16 is increased over thatin the embodiments in FIGS. 1 through 8.

Referring to FIG. 18, substrate 10 is provided. Next, substrate 10 isetched to form trenches 14 and semiconductor strips 12. Depth D1 oftrenches 14 may be in the range between about 100 nm and about 170 nm.Next, referring to FIG. 19, STI regions 30 are formed. The formationprocess includes the filling of a dielectric material in trenches 14(FIG. 18), followed by a CMP. The material of STI regions 30 may beselected from the same candidate materials of STI regions 20 in FIGS. 1through 8, and may include an oxide formed using FCVD or spin on.

Referring to FIG. 20, STI regions 30 are recessed, with the top portionsof STI regions 30 etched, to form trenches 32. The bottom portions ofSTI regions 30 remain after the etching. Depth D3 of trenches 32 may bein the range between about 40 nm and about 100 nm. In the subsequentstep, as shown in FIG. 21, dielectric liner 16 is formed on the exposedsidewalls and the top surfaces of semiconductor strips 12. Dielectricliner 16 further extends to the bottoms of trenches 32.

FIGS. 22 through 26 illustrate the remaining processes for the formationof FinFETs 128 and 228. The subsequent process steps and the materialsare essentially the same as shown in FIGS. 4 through 8. The details ofthe process details and the materials of the related components may thusbe found in the embodiments shown in FIGS. 4 through 8, and are notrepeated herein. A brief description is provided as follows. FIGS. 22through 23 illustrate the removal of dielectric liner 16 from deviceregion 200. Dielectric liner 16 is left in device region 100. Next, asshown in FIG. 24, STI regions 20 are formed. FIG. 25 illustrates therecessing of STI regions 20 to form semiconductor fins 22. Gatedielectrics 24A and 24B and gate electrode 26A and 26B are then formed,as shown in FIG. 26. Source and drain regions (not shown) are thenformed to finish the formation of FinFETs 128 and 228.

FIGS. 27 through 36 illustrate the formation of complementary FinFETs inaccordance with yet alternative embodiments. These embodiments aresimilar to the embodiments in FIGS. 9 through 17, except that before theformation of dielectric liners 16 and 16′ and STI regions 20, lower STIregions 30 are formed to fill the bottom portions of trenches 14,leaving the top portions of trenches 14 not filled. By filling thebottom portions of trenches 14 with STI regions 30, dielectric liners 16and 16′ (FIG. 36) are formed in the trenches with a smaller aspect ratiothan the trenches in the embodiments in FIGS. 9 through 17. Thehorizontal portions of dielectric liners 16 and 16′ are thus closer tothe overlying semiconductor fins, and the stresses applied by dielectricliners 16 and 16′ is increased over that in the embodiments in FIGS. 9through 17.

Referring to FIG. 27, substrate 10 is provided. Next, substrate 10 isetched to form trenches 14 and semiconductor strips 12. Depth D1 oftrenches 14 may be in the range between about 100 nm and about 170 nm.Next, referring to FIG. 28, STI regions 30 are formed. The formationprocess includes the filling of a dielectric material in trenches 14(FIG. 18), followed by a CMP. The material of STI regions 30 may beselected from the same candidate materials of STI regions 20 in FIGS. 1through 8, and may include an oxide formed using FCVD or spin on.

Referring to FIG. 29, STI regions 30 are recessed, with the top portionsof STI regions 30 etched, to form trenches 32. The bottom portions ofSTI regions 30 remain after the etching. Depth D3 of trenches 32 may bein the range between about 40 nm and about 100 nm. In the subsequentstep, as shown in FIG. 30, dielectric liner 16 is formed on the exposedsidewalls and the top surfaces of semiconductor strips 12. Dielectricliner 16 further extends to the bottoms of trenches 32.

FIGS. 31 through 36 illustrate the remaining processes for the formationof FinFETs 128 and 228. The subsequent process steps and the materialsare essentially the same as shown in FIGS. 10 through 17. The details ofthe process details and the materials of the related components may thusbe found in the embodiments shown in FIGS. 10 through 17, and are notrepeated herein. A brief description is provided as follows. FIGS. 31and 32 illustrate the removal of dielectric liner 16 from device region200. Dielectric liner 16 is left in device region 100. Next, as shown inFIGS. 33 and 34, dielectric liner 16′ is formed in devices regions 100and 200 (FIG. 33), and is then removed from device region 100 (FIG. 34).Next, as shown in FIG. 35, STI regions 20 are formed. FIG. 35 alsoillustrate the recessing of STI regions 20 to form semiconductor fins22. Gate dielectrics 24A and 24B and gate electrode 26A and 26B are thenformed, as shown in FIG. 36. Source and drain regions (not shown) arethen formed to finish the formation of FinFETs 128 and 228.

The embodiments of the present disclosure have some advantageousfeatures. By applying/blocking stresses through dielectric liners, whichhave different schemes in p-type and n-type FinFET regions, desirablestresses may be applied on the p-type and n-type FinFETs to improve theperformance of the FinFETs.

In accordance with some embodiments, an integrated circuit deviceincludes a substrate having a first portion in a first device region anda second portion in a second device region. A first semiconductor stripis in the first device region. A dielectric liner has an edge contactinga sidewall of the first semiconductor strip, wherein the dielectricliner is configured to apply a compressive stress or a tensile stress tothe first semiconductor strip. An STI region is over the dielectricliner, wherein a sidewall and a bottom surface of the STI region is incontact with a sidewall and a top surface of the dielectric liner.

In accordance with other embodiments, an integrated circuit deviceincludes a substrate having a first portion in a first device region anda second portion in a second device region, a first semiconductor stripin the first device region, and a first dielectric liner including anedge contacting a sidewall of the first semiconductor strip, wherein thefirst dielectric liner is configured to apply a stress to the firstsemiconductor strip. The integrated circuit device further includes afirst STI region over the first dielectric liner, wherein a sidewall anda bottom surface of the first STI region is in contact with a sidewalland a top surface of the first dielectric liner. The integrated circuitdevice further includes a second semiconductor strip in the seconddevice region, and a second STI region over the second dielectric liner.The first STI region and the second STI region are formed of a samehomogenous material, wherein a sidewall and a bottom surface of thesecond STI region is in contact with a sidewall and a top surface of thesecond dielectric liner.

In accordance with yet other embodiments, a method includes etching asemiconductor substrate to form a first trench in a first device regionand a second trench in a second device region, wherein portions of thesemiconductor substrate form a first semiconductor strip with a sidewallexposed to the first trench, and a second semiconductor strip with asidewall exposed to the second trench. The method further includesforming a first dielectric liner on the sidewall of the firstsemiconductor strip and the sidewall of the second semiconductor strip,removing the first dielectric liner from the second device region,wherein the first dielectric liner is left in the first device region,and forming a first STI region over the first dielectric liner and inthe first trench, wherein a sidewall and a bottom surface of the firstSTI region is in contact with a sidewall and a top surface of the firstdielectric liner. The method further includes forming a second STIregion in the second trench, wherein the first STI region and the secondSTI region are formed simultaneously.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the embodiments as defined by the appended claims. Moreover,the scope of the present application is not intended to be limited tothe particular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods and steps described in thespecification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. In addition, each claim constitutes a separateembodiment, and the combination of various claims and embodiments arewithin the scope of the disclosure.

What is claimed is:
 1. An integrated circuit device comprising: asemiconductor substrate comprising a first portion in a first deviceregion and a second portion in a second device region; a firstsemiconductor strip in the first device region; a second semiconductorstrip in the second device region; a first dielectric liner comprisingan edge contacting a sidewall of the first semiconductor strip, whereinthe first dielectric liner is configured to apply a first stress to thefirst semiconductor strip; a first Shallow Trench Isolation (STI) regionover the first dielectric liner; and a second dielectric linercomprising an edge contacting a sidewall of the second semiconductorstrip, wherein the second dielectric liner is configured to block anapplication of a second stress different from the first stress to thesecond semiconductor strip by a second STI region over the seconddielectric liner.
 2. The integrated circuit device of claim 1 furthercomprising: a third STI region; a third semiconductor strip in the firstdevice region of the semiconductor substrate; a third dielectric lineroverlapped by a first portion of the third STI region, wherein the firstdielectric liner and the third dielectric liner are formed of a samefirst material, and apply a same type of stress on the thirdsemiconductor strip, and the third dielectric liner contacts a sidewallof the third semiconductor strip; and a fourth dielectric lineroverlapped by a second portion of the third STI region, wherein thesecond dielectric liner and the fourth dielectric liner are formed of asame second material.
 3. The integrated circuit device of claim 2,wherein the third dielectric liner contacts the fourth dielectric liner.4. The integrated circuit device of claim 1, wherein a bottom surface ofthe first dielectric liner contacts a top surface of the semiconductorsubstrate.
 5. The integrated circuit device of claim 1 furthercomprising a first additional STI region overlapped by, and contacting,the first dielectric liner, wherein the first additional STI regioncontacts the sidewall of the first semiconductor strip.
 6. Theintegrated circuit device of claim 5 further comprising a secondadditional STI region overlapped by, and contacting, the seconddielectric liner, wherein the second additional STI region contacts thesidewall of the second semiconductor strip.
 7. The integrated circuitdevice of claim 1, wherein the first dielectric liner is configured toapply a compressive stress to the first semiconductor strip, with thecompressive stress having a magnitude higher than about 300 MPa.
 8. Theintegrated circuit device of claim 7, wherein the second dielectricliner is comprised of a material that has a Young's modulus higher than100 GPa.
 9. An integrated circuit device comprising: a substratecomprising a first portion in a first device region and a second portionin a second device region; a first semiconductor strip in the firstdevice region; a first dielectric liner comprising an edge contacting asidewall of the first semiconductor strip, wherein the first dielectricliner is configured to apply a compressive stress to the firstsemiconductor strip, wherein the first dielectric liner is made of afirst homogeneous material; a first Shallow Trench Isolation (STI)region over the first dielectric liner, wherein a sidewall and a bottomsurface of the first STI region is in contact with a sidewall and a topsurface, respectively, of the first dielectric liner; a secondsemiconductor strip in the second device region; a second dielectricliner comprising an edge contacting a sidewall of the secondsemiconductor strip, wherein the second dielectric liner is configuredto apply a tensile stress to the second semiconductor strip, wherein thesecond dielectric liner is made of a second homogeneous material; and asecond STI region, wherein a sidewall and a bottom surface of the secondSTI region is in contact with a sidewall and a top surface of the seconddielectric liner.
 10. The integrated circuit device of claim 9 furthercomprising: a third STI region overlapped by the first dielectric liner;and a fourth STI region overlapped by the second dielectric liner. 11.The integrated circuit device of claim 10 further comprising a thirdsemiconductor strip, wherein each of the first dielectric liner and thethird STI region comprises a first end contacting the firstsemiconductor strip, and a second end contacting the third semiconductorstrip.
 12. The integrated circuit device of claim 9, wherein a bottomsurface of the first dielectric liner is in physical contact with a topsurface of the substrate.
 13. The integrated circuit device of claim 9further comprising: a first gate dielectric on a top surface andsidewalls of the first semiconductor strip; a first gate electrode onthe first gate dielectric, wherein the first gate dielectric and thefirst gate electrode are portions of a first transistor; a second gatedielectric on a top surface and sidewalls of the second semiconductorstrip; and a second gate electrode on the second gate dielectric,wherein the second gate dielectric and the second gate electrode areportions of a second transistor, and the first transistor and the secondtransistor are of opposite conductivity types.
 14. The integratedcircuit device of claim 9, wherein the first STI region has a topsurface recessed lower than top edges of the first dielectric liner. 15.An integrated circuit device comprising: a first semiconductor strip anda second semiconductor strip over a same semiconductor substrate; afirst dielectric liner and a second dielectric liner contacting a firstsidewall of the first semiconductor strip and a second sidewall of thesecond semiconductor strip, respectively; a first Shallow TrenchIsolation (STI) region comprising a third sidewall and a fourth sidewallcontacting sidewalls of the first dielectric liner and the seconddielectric liner, respectively, wherein the first dielectric liner andthe second dielectric liner are configured to apply different stressesto the first semiconductor strip and the second semiconductor strip; anda second STI region under and overlapped by the first dielectric linerand the second dielectric liner.
 16. The integrated circuit device ofclaim 15, wherein the first STI region comprises a first portion aboveand overlapping a bottom portion of the first dielectric liner, and asecond portion above and overlapping a bottom portion of the seconddielectric liner.
 17. The integrated circuit device of claim 15, whereinthe first dielectric liner physically contacts the second dielectricliner.
 18. The integrated circuit device of claim 15 further comprising:a first gate dielectric on a top surface and sidewalls of the firstsemiconductor strip, wherein a portion of the first gate dielectricoverlaps the first STI region; a first gate electrode on the first gatedielectric; a second gate dielectric on a top surface and sidewalls ofthe second semiconductor strip, wherein a portion of the second gatedielectric overlaps the first STI region; and a second gate electrode onthe second gate dielectric.
 19. The integrated circuit device of claim18, wherein the first gate electrode and the second gate electrode arephysically separated from each other by a gap.
 20. The integratedcircuit device of claim 15 further comprising: a third dielectric linerapplying a same type of stress as the first dielectric liner to thefirst semiconductor strip, wherein the third dielectric liner contacts afifth sidewall of the first semiconductor strip, wherein the firstsidewall and the fifth sidewall are opposite sidewalls of the firstsemiconductor strip; and a third semiconductor strip, wherein the thirddielectric liner further contacts a sidewall of the third semiconductorstrip.